<div>You are dead on. He wants his panning to be different based on where he is at.</div>
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<div>I am using the WMS service from Nasa and then I am layering a single tile image when they get to a certain resolution. So basically their API offers me a way to pass in an Upper Left lat/lon and lower right lat/lon and it returns an image. I can pass in projection as well.
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<div>My map provider is GEX/Digital Globe but their crack at an openlayers solution is not working for me. If I didn't need markers, line features, and any different resolutions it would work fine as a navigation layer. It is full of bugs. It is not a WMS service but their own layer. They must be in the middle of their merger because they are not very helpful.
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<div>Thanks for the information. It is SOOO helpful.</div>
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<div>Linda Rawson<br> </div>
<div><span class="gmail_quote">On 9/30/07, <b class="gmail_sendername">Christopher Schmidt</b> <<a href="mailto:crschmidt@metacarta.com">crschmidt@metacarta.com</a>> wrote:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">On Sun, Sep 30, 2007 at 01:30:14PM -0600, Linda Rawson wrote:<br>> I think I can get this one but if someone has a formula to help me that
<br>> would be great.<br>><br>> Basically he uses the panning tool. The north, south, east, west tool. So<br>> when he goes east he does not want to evenly go to the next square. He<br>> wants to go to the next square based on a sphere. If he was on the equator
<br>> then the pixels would be correct. But if he is in say Canada he wants to<br>> panning tool to go to the next square in the sphere. I hope this is making<br>> sense.<br><br>Okay, I think I get it.<br><br>The world is a kinda-spheroid like thing. The default OpenLayers
<br>projection is a lon/lot geographic coordinate system -- this means that<br>50 pixels north is 50 * map.resolution degrees north. However, what<br>number of *meters* that is on the ground is variable, based on where the
<br>lat/lon are.<br><br>So, in order to make the spheroid world a 2D plane, we 'project' it. The<br>lon/lat geographic projection is just one option here -- others are, for<br>example, mercator, or peters equal area, etc.
<br><br>It sounds like the person you are talking to wants a projected map.<br>Depending on the type of things this person cares about, this may be<br>easy or hard.<br><br><a href="http://openlayers.org/dev/examples/spherical-mercator.html">
http://openlayers.org/dev/examples/spherical-mercator.html</a> is a<br>set of projected maps. You can see that the WMS service is providing<br>data not according to lat/lon, but according to projected units. To the<br>user, it doesn't really make any difference, if they don't see the units
<br>-- they just know that they go up, and as they go up, the amount of<br>latitude/longitude they go up by every time they hit the button is<br>different, instead of the same.<br><br>It's not really clear to me who 'the map providers' are in this case.
<br>Does he or she mean Google? If so, then the sphericalMercator support in<br>2.5 is probably just the kind of thing he is looking for, as it will let<br>you lay images on top of these and tile them properly. If the customer
<br>is talking about some other data provider... well, it's hard to know<br>what exactly he (or she) means.<br><br>Perhaps with a bit more information about the scenario you are exploring<br>would be helpful here.<br>
<br>> I create the image based on the lat/lon coordinates passed to me with open<br>> layers. The mapping service I use just needs the upper left and lower right<br>> corners to return the images.<br><br>Are you just using one layer? Where is the image coming from? Do you
<br>have a commercial base layer? something else?<br><br>Regards,<br>--<br>Christopher Schmidt<br>MetaCarta<br></blockquote></div><br>